Are we alone in the universe? It’s a fundamental question that we currently do not know the answer to. If there is intelligent life in the universe other than ourselves, where is the evidence? The following is a top 10 of possible evidence for Extra-Terrestrial Intelligence (ETI). Let me know in the comments if there are others to add to the list.

10) Wow Signal

On 15 August, 1977, a burst of radio waves was detected by the now dismantled Big Ear radio telescope of Ohio State University. The person who spotted it, astronomer Jerry Ehman, was so surprised that he scribbled “Wow” on the print-out. The Wow signal, as it has become known, is often described as our best candidate for a signal from an ETI.

This unusually strong, narrowband radio signal lasted 72 seconds. The duration matches the time it takes the Big Ear scanning beam to survey a given point in deep space, thus indicating that the signal’s was not a result of Earthly radio interference. The signal was also unusual in that it was intermittent; it appears to it have been “turned off” between two scans of the same location, just minutes apart. The signal has never been explained. Was this strong, focused, intermittent deep-space signal evidence of ETI? The fact that the signal has not since been detected make this a frustrating piece of potential evidence.

9) Drake Equation

In 1961, a small group of astrophysicists gathered at the National Radio Astronomy Observatory, Green Bank, WV. Frank Drake presented his equation to estimate the number of intelligent, communicating civilizations in our galaxy:

N = R* x fp x ne x fe x fi x fc x L

R* = rate of star formation in our galaxy
fp = fraction of stars with planetary systems ne = number of habitable planets per planetary system fe = fraction with life evolved
fi = fraction where life develops intelligence
fc = fraction which are willing and able to communicate
L = lifetime of such civilizations (in years)

The values to plug into this equation vary widely depending on who you ask. It has also been noted that the first 6 terms can equate to close to 1, so that we can approximate by saying that N = L.

The number of civilizations in our galaxy with the ability to communicate is equal to the lifetime of such civilizations.

So, depending on the value of L, N can range from about 100 to several billion. Thus, there may be a million or so civilizations within our own galaxy with whom we might communicate. Since astronomers estimate there are over 100 billion galaxies in our universe, that gives at least 100 million, billion technological civilizations in the universe. Note also that this equation only estimates the number of civilizations that are formed via planetary evolution, and does not include other forms of life less similar to our own. While this is not direct evidence, it is a very compelling statistical clue that ETIs do exist in the universe.

8 ) 2004 XR190

In 2004, astronomers discovered a very unusual object in the outer solar system. This object, 2004 XR190 (known affectionately as ‘Buffy’) is unusual in that it’s orbit is almost perfectly circular and at a 47 degree angle to the ecliptic plane (where most solar system objects lie) making it the most tilted object in the solar system. Current theories of the solar system’s formation cannot account for this odd orbit. 2004 XR190 was very hard to detect due to the fact that it rarely passes thru the ecliptic plane.

2004 XR190 is a good candidate for a sentinel object. Sentinel objects were first proposed by Arthur C Clarke in 1948. Sentinel objects are created by ETIs. Their purpose is to lie dormant in an area of space until the civilization there has reached a certain level of technological sophistication and is able to detect and interact with the object.

7) Pulsars

Pulsars are objects in the universe that are emitting powerful “lighthouse beams” of radio waves and light flashing through the Universe. When first discovered in 1967, scientists first reaction was that these beacons could be signals from an ETI (in fact the initial name for the pulsar was ‘LGM-1’ for ‘little-green-men’ ). The scientific community has since settled on the model that pulsars are spinning, superdense neutron stars that emit pulses via ‘cones of emission’, created by magnetic fields. There are however some problems with this model, as noted by this astronomer:

Neutron stars are the densest objects in the Universe and provide important physical tests of our most basic understanding of matter. Much of this theory is based on a belief that we could accurately estimate their ages. Our research indicates that these objects may be 10 times older than we thought, and this could force much re-evaluation … This means that much of what we thought we understood about the physics of pulsars and neutron stars may be wrong

Bryan Gaensler, Astronomer at the Harvard-Smithsonian Center for Astrophysics, 2000.

In fact, the Neutron star theory has required ever more complex models in order to account for the observed data. Pulsars have a strong frequency and also fine grain modulations within that frequency. It has been postulated that these modulations may encode information. The possibility remains that pulsars may be artificially created communication beacons. In his book, The Talk of the Galaxy, Dr. Paul LaViolette shows how new high-resolution recordings of pulsar signals reveal features that are inconsistent with the long-standing “neutron star lighthouse” pulsar model. He has even proposed that the position of certain powerful pulsars may encode the mathematical constant Pi, indicating that pulsars have been created by super-advanced ETIs.

6) Hallucinogenic Fungi

Fungi is well known to be very different to any other form of life on earth. Fungi form the fifth Kingdom of life on earth, being neither plant, animal, microbes or protozoa. Fungal spores are incredibly resilient to extreme conditions of temperature and radiation, and have been recorded to thrive in space. For example, certain types of fungi have become problematic in the Mir Space Station, growing in air-conditioning units and corroding materials. These facts lead to the possibility that fungus may have an extraterrestrial origin, possibly being transmitted to Earth via spores in an asteroid or comet.

Many types of fungi have profound mind-altering effects when consumed by humans. Hallucinogenic Fungi produces radically different perceptual brain states in humans via a process that is not fully understood. It only takes a miniscule quantity of these fungal molecules to enter the bloodstream, and the human brain is somehow ‘de-tuned’ from every-day reality, instead focusing on an alternate perception of the universe.

Hallucinogenic Fungi is worshipped by many shamanic tribes across the earth. It has been postulated that our pre-literate ancestors once worshipped ‘the divine mushroom’, and that hallucinogenic fungi was instrumental in developing human intelligence, specifically language. Many shamanic religions treat their fungi as an intelligence that can be interacted with via the hallucinogenic state. For example the Bwiti tribe in Gabon believe that iboga is a ‘super-concious spiritual entity that guides mankind’.

Some fungi is know to produce states where we can directly communicate with seemingly alien intelligences (for example the ‘self-transforming machine elves’ associated with DMT). Terence McKenna has proposed that hallucinogenic fungi may be an alien technology, “seeded” on Earth by non-human intelligence, as part of a “biological communication strategy”, in order to alter the perceptive processes of the human mind so that it may receive messages being transmitted to us. It is also conceivable that fungi is in itself intelligent, meaning that ETIs are living among us undetected right now.

5) First Hand UFO and Abduction Accounts

UFO accounts have been around for a long time. Here’s an example from the Old Testament:

4 And I looked, and, behold, a whirlwind came out of the north, a great cloud, and a fire infolding itself, and a brightness was about it, and out of the midst thereof as the color of amber, out of the midst of the fire.
5 Also out of the midst thereof came the likeness of four living creatures. And this was their appearance; they had the likeness of a man.
6 And every one had four faces, and every one had four wings.
19 And when the living creatures went, the wheels went by them: and when the living creatures were lifted up from the earth, the wheels were lifted up.


Some modern UFO accounts are quite compelling, for example there are many radio transcripts from airline pilots that describe encounters with UFOs in detail. Here is a pilot describing a prolonged encounter over Alaska in 1986:

Most unexpectedly two space ships stopped in front of our face, shooting off lights…The inside cockpit shined brightly and I felt warm in the face.

Captain Kenju Terauchi, Japan Airlines 747 pilot

There is lots of fakery and fraud in the UFO industry, but it remains true that there are many seemingly rational people who have had first hand experience of events that do not fit in with our normal expectations.

If extraterrestrial encounters are happening on earth, why is there no photographic proof? The fact that there is no photographic proof does not mean that such encounters do not happen. For comparison, there are no photos of lightning striking a human, although lightning kills around 100 people per year, in the U.S. alone.

Why does it seem like recent alien abduction accounts only happen to people in rural parts of America? One explanation may be that ETIs only like to abduct people that are not in close proximity to other humans. Are UFO abductions happening in other rural parts of the world?

4) Prehistoric Astronomical Structures (Stonehenge, Nazcar lines, Easter Island Statues)

There is some good evidence for ancient societies having contact with ETIs. There are a number of prehistoric mega-structures surviving today, that seem to encode very advanced astronomical knowledge. If advanced ETIs had contacted humanity in pre-historic times, they would almost certainly be regarded as gods. Many religions today contain references to visitors from the stars and vehicles traveling through the air. Also, some ancient artworks can be interpreted as depicting alien lifeforms and aircraft. The idea that Earth has been visited by extra-terrestrials in the past was popularized by Erich von Däniken in the 1970’s. Däniken has since fallen out of fashion and is now seen by many as a fraud.

One particularly intriguing ancient structure is the Nazca lines, created around 200 BC. These are a set of gigantic patterns drawn into the earth on a desert plateau in southern Peru. The patterns can only be observed from a position high above the Earth. Some of the patterns seem to resemble primitive landing strips.

3) Historical Great Teachers

Throughout recorded history there has been a small number of incredibly influential teachers. Examples include Jesus, Buddha, Newton and Einstein. These teachers created whole new ways of thinking that were very beneficial to humankind. They introduced ideas that were so advanced and radically different to their contemporaries’ it seems possible that they had access to outside information.

One theory is that these great teachers were guided by, or were ETIs. Their purpose seems to have been to guide humanity in a positive direction.

2) Our Existence

Our existence in the universe is a mystery. Nobody knows how life on earth was formed. Could it be that our own existence is evidence for ETIs?

In 1973, Professor Francis Crick (co-discoverer of the structure of DNA), proposed the theory of directed panspermia. This suggests that the seeds of life may have been purposely spread by an advanced extraterrestrial civilization. One way to achieve this would be to fire small grains of DNA across space. It is well known that simple lifeforms can exist in space (for example scientists found living Earth bacteria on a Lunar lander that had been exposed to the moon’s vacuum for years).

Another, more extreme theory is that super-advanced ETIs may be creating and manipulating universes in order to create other intelligent lifeforms. The fact that our universe is hospitable to human life seems statistically very unlikely. If any of the fundamental physical constants (such as the speed of light) were slightly different, then life as we know it would not be possible. One current theory states that there may be a ‘multiverse’ of universes, each with its own set of fundamental physical constants. These universes are connected via black holes. What appears to us as a black hole is in fact a portal to a new ‘baby universe’ that is spawned via a local big bang.

It is concievable that a super-advanced ETI that has mastered the power of black holes could be spawning universes and manipulating their physical constants in order to nurture further intelligent life. A recent study by Avi Loeb, states that black holes may in fact be the seed for galactic formation, and that black holes may have appeared in our universe far earlier than expected. Could this be further evidence of ETIs fine-tuning our universe for the creation of intelligent life?

1) Absence of Evidence Is Not Evidence of Absence

Many people refuse to believe in ETIs until the proverbial ‘alien spaceship lands on the Whitehouse lawn’. These people are proponents of Fermi’s principal, which states that lack of evidence conclusively demonstrates the non-existence of extraterrestrial civilizations.

Contrary to this viewpoint, Carl Sagan has famously noted that ‘absence of evidence is not evidence of absence’. The idea that ETIs would announce themselves to us is based on the assumption that ETIs would act in a similar manner to ourselves. The idea that ETIs would be easily detectable by us is again quite presumptuous. There are many reason why ETIs may not be detectable to us.

Firstly, we may not even recognize the activities of very advanced extraterrestrial civilizations, as stated here:

The manifestations of very advanced civilizations may not be in the least apparent to a society as backward as we, any more than an ant performing his anty labors by the side of a suburban swimming pool has a profound sense of the presence of a superior technical civilization all around him.

Carl Sagan

A second possibility is the Zoo hypothesis. This hypothesis holds that ETIs are aware of us but choose not to reveal themselves to us for a variety of possible reasons.

A third possibility is that ETI societies may transcend our universe once they hit a certain level of advancement. ETIs may upload themselves to infinite virtual worlds. The Matrioshka brain has been proposed as one way to do this. Matrioshka brains would be undetectable from large distances. Another way to transcend would be to physically move into a new universe. For a super advanced civilization it may be possible to create a local “baby universe” by manipulating black holes. This civilization could then colonize the newly created universe.